Formation Of Residues Research Articles

Enzymatic Formation of an Aminovinyl Cysteine Residue in Ribosomal Peptide Natural Products.

The carboxyl-terminal (C-terminal) S-[(Z)-2-aminovinyl]-cysteine (AviCys) analogs have been identified in four families of ribosomally synthesized and post-translationally modified peptides (RiPPs): lanthipeptides, linaridins, thioamitides, and lipolanthines. Within identified biosynthetic pathways, a highly reactive enethiol intermediate, formed through an oxidative decarboxylation catalyzed by a LanD-like flavoprotein, can undergo two types of cyclization: a Michael addition with a dehydroamino acid or a coupling reaction initiated by a radical species. The collaborative actions of LanD-like proteins with diverse enzymes involved in dehydration, dethiolation or cyclization lead to the construction of structurally distinct peptide natural products with analogous C-terminal macrocyclic moieties. This concept summarizes existing knowledge regarding biosynthetic pathways of AviCys analogs to emphasize the diversity of biosynthetic mechanisms that paves the way for future genome mining explorations into diverse peptide natural products.

A low-temperature photoresist-based film-profile engineering scheme for fabricating bottom- and double-gated indium–gallium–zinc oxide TFTs

We proposed a novel low-temperature (<110 °C) process scheme based on the film-profile engineering technique for fabricating indium–gallium–zinc oxide thin-film transistors (TFTs) with both bottom-gated (BG) and double-gated (DG) configurations. An organic photoresist (PR) suspended bridge is constructed to shadow the depositing species during the deposition processes of the bottom gate-oxide, channel, and source/drain metal films. An Al2O3 layer deposited at 110 °C using atomic-layer deposition is employed as the bottom gate-oxide layer. Such a low-temperature process allows us to deposit the Al2O3 layer following the formation of the PR suspended bridge, preventing the formation of organic residues between the gate-oxide and channel layers. As a result, excellent device performance in terms of field-effect mobility of 12.1 cm2 V−1 s−1 and subthreshold swing of 141 mV/dec is achieved. Our proposed low-temperature process scheme is readily applicable for fabricating DG TFTs which show substantial enhancements in driving currents.

Fate of dimethylsilanediol (DMSD) in soil-plant systems

Dimethylsilanediol (DMSD) is the degradation product of methylsiloxane polymers and oligomers such as volatile cyclic methylsiloxanes (cVMS). To better understand the environmental fate of this key degradation product, we conducted a three-part study on the movement of DMSD in soil. The objective of this third and final study was to determine the fate of DMSD in soil-plant systems under constant irrigation. Soil columns were constructed using two soils with the upper 20 cm layers spiked with 14C-labeled DMSD. Corn seedlings were transplanted into the soil columns and placed in a field plot underneath a transparent cover that prevented rainwater from reaching the soil columns while allowing soil water to be volatilized freely. The soil-plant columns were regularly irrigated with known amounts of DMSD-free plant growth solution to sustain the plant growth. At pre-determined time intervals (15–67 days), the plant and soil columns were sectioned and the distribution of 14Corganosilicon species in the soil profile and plant parts was determined using a combination of Liquid Scintillation Counting and High-Performance Liquid Chromatography-Flow Scintillation Analysis, while soil water loss was determined gravimetrically. It was found that the majority (>92 %) of DMSD initially spiked into the soil was removed from the soil-plant systems. Although DMSD was transported from the soil to the plant, it was subsequently volatilized from the plant via transpiration, with only a small fraction (∼5%) remaining at the conclusion of the experiments. In addition, little non-extractable DMSD was found in the top layer of soil in the soil-plant systems, suggesting that the air-drying of soil is a necessary pre-condition for the formation of such non-extractable silanol residue on topsoil.

Nitrogen-fertilizer addition to an agricultural soil enhances biogenic non-extractable residue formation from 2-13C,15N-glyphosate

Glyphosate and nitrogen (N) or (P) phosphorus fertilizers are often applied in combination to agricultural fields. The additional P or N supply to microorganisms might drive glyphosate degradation towards sarcosine/glycine or aminomethylphosphonic acid (AMPA), and consequently determine the speciation of non-extractable residues (NERs): harmless biogenic NERs (bioNERs) or potentially hazardous xenobiotic NERs (xenoNERs). We therefore investigated the effect of P or N-fertilizers on microbial degradation of glyphosate and bioNER formation in an agricultural soil. Four different treatments were incubated at 20 °C for 75 days as follows; I: no fertilizer (2-13C,15N-glyphosate only, control), II: P-fertilizer (superphosphate + 2-13C,15N-glyphosate, effect of P-supply), III: N-fertilizer (ammonium nitrate + 2-13C,15N-glyphosate, effect of N-supply) and IV: 15N-fertilizer (15N-ammonium nitrate + 2-13C-glyphosate, differentiation between microbial assimilations of 15N: 15N-fertilizer versus 15N-glyphosate). We quantified 13C or 15N in mineralization, extractable residues, NERs and in amino acids (AAs). At the end, mineralization (36–41 % of the 13C), extractable 2-13C,15N-glyphosate/2-13C-glyphosate (0.42–0.49 %) &15N-AMPA (1.2 %), and 13C/15N-NERs (40–43 % of the 13C, 40–50 % of the 15N) were comparable among treatments. Contrastingly, the 15N-NERs from 15N-fertlizer amounted to only 6.6 % of the 15N. Notably, N-fertilizer promoted an incorporation of 13C/15N from 2-13C,15N-glyphosate into AAs and thus the formation of 13C/15N-bioNERs. The 13C/15N-AAs were as follows: 16–21 % (N-fertilizer) > 11–13 % (control) > 7.2–7.3 % (P-fertilizer) of the initially added isotope. 2-13C,15N-glyphosate was degraded via the sarcosine/glycine and AMPA simultaneously in all treatments, regardless of the treatment type. The percentage share of bioNERs within the NERs in the N-fertilized soil was highest (13C: 80–82 %, 15N: 100 %) compared to 53 % (13C &15N, control) and to only 30 % (13C &15N, P-fertilizer). We thus concluded simultaneous N & glyphosate addition to soils could be beneficial for the environment due to the enhanced bioNER formation, while P & glyphosate application disadvantageous since it promoted xenoNER formation.

Bioinspired phosphorus-free and halogen-free biomass coatings for durable flame retardant modification of regenerated cellulose fibers

Inspired by mussel adhesion and intrinsic flame retardant alginate fibers, a biomass flame retardant (PPCA) containing adhesive catechol and sodium carboxylate structure (-COO−Na+) based on biomass amino acids and protocatechualdehyde was designed to prepare flame retardant Lyocell fibers (Lyocell@PPCA@Na). Furthermore, through the substitution and chelation of metal ions by PPCA in the cellulose molecular chain, flame retardant Lyocell fibers chelating copper and iron ions (Lyocell@PPCA@Cu, Lyocell@PPCA@Fe) were prepared. Compared with the original sample, the peak heat release rate (PHRR) and total heat release (THR) for modified Lyocell fibers were significantly reduced. In addition, the modified sample exhibited a certain flame retardant durability. TG-FTIR analysis showed that the release of flammable gaseous substances was inhibited. The introduction of Schiff bases and aromatic structures in PPCA, as well as the decomposition of carboxylic metal salts were beneficial for the formation of char residue containing metal carbonates and metal oxides to play the condensed phase flame retardant effect. This work develops a new idea for the preparation of eco-friendly flame retardant Lyocell fibers without the traditional flame retardant elements such as P, Cl, and Br.

Characterization of a LanC-free pathway for the formation of an ll-MeLan residue and an alloAviMeCys residue in the newly identified class V lanthipeptide triantimycins.

The thioether-connected bis-amino acid lanthionine (Lan) residues are class-defining residues of lanthipeptides. Typically, the cyclization step of lanthionine formation, which relies on the addition of a cysteine to an unsaturated dehydroamino acid, is directed either by a standalone cyclase LanC (class I) or by a cyclase domain (class II-IV). However, the pathways of characterized class V members often lack a known cyclase (domain), raising a question on the mechanism by which their multi-macrocycle systems are formed. Herein, we report a new RiPP gene cluster in Streptomyces TN 58, where it encodes the biosynthesis of 3 distinct class V lanthipeptides-termed triantimycins (TAMs). TAM A1∼A3 share an N-terminal ll-MeLan residue, and only TAM A1 contains an additional internal ll-Lan residue. TAM A1 also has a C-terminal (2S, 3R)-S-((Z)-2-aminovinyl)-3-methyl-d-cysteine (alloAviMeCys) residue, which is distinct from the previously reported (2S, 3S)-AviMeCys residue in other RiPPs. Gene deletion, heterologous coexpression, and structural elucidation demonstrated that the cyclization for an ll-MeLan formation occurs spontaneously and is independent of any known lanthionine cyclase. This study provides a new paradigm for lanthionine formation and facilitates genome mining and engineering efforts on RiPPs containing (Me)Lan and (allo)Avi(Me)Cys residues.

Smart controlled-release nanopesticides based on metal-organic frameworks.

The practical utilization rates of conventional pesticide formulations by target organisms are very low, which results in the pollution of ecological environments and the formation of pesticide residues in agricultural products. Water-based nanopesticide formulations could become alternative and effective formulations to eventually resolve the main issues of conventional pesticide formulations. In this feature article, we describe the design concept of smart (stimuli-responsive) controlled-release nanopesticides, which are created toward hierarchical targets (pests, pathogens, and foliage) in response to multidimensional stimuli from physiological and environmental factors (such as sunlight) of target organisms and plants, for achieving enhanced insecticidal and fungicidal efficacies. The pore sizes and functionalities of metal-organic frameworks (MOFs) can be fine-tuned through the choice of metal-containing units and organic ligands. Tailor-made MOF nanoparticles with large microporous or mesoporous sizes, as well as good biocompatibility and high thermal, mechanical, and chemical durabilities, are used to load pesticides within these pores followed by coating of plant polyphenols and natural polymers for stimuli-responsive controlled pesticide release. This feature article highlights our works on smart controlled-release MOF-based nanopesticides and also includes related works from other laboratories. The future challenges and promising prospects of smart controlled-release MOF-based nanopesticides are also discussed.

Dehydroamino acid residues in bioactive natural products.

Covering: 2000 to up to 2023α,β-Dehydroamino acids (dhAAs) are unsaturated nonproteinogenic amino acids found in a wide array of naturally occurring peptidyl metabolites, predominantly those from bacteria. Other organisms, such as fungi, higher plants and marine invertebrates, have also been found to produce dhAA-containing peptides. The α,β-unsaturation in dhAAs has profound effects on the properties of these molecules. They display significant synthetic flexibility, readily undergoing reactions such as Michael additions, transition-metal-catalysed cross-couplings, and cycloadditions. These residues in peptides/proteins also exhibit great potential in bioorthogonal applications using click chemistry. Peptides containing contiguous dhAA residues have been extensively investigated in the field of foldamers, self-assembling supermolecules that mimic biomacromolecules such as proteins to fold into well-defined conformations. dhAA residues in these peptidyl materials tend to form a 2.05-helix. As a result, stretches of dhAA residues arrange in an extended conformation. In particular, peptidyl foldamers containing β-enamino acid units display interesting conformational, electronic, and supramolecular aggregation properties that can be modulated by light-dependent E-Z isomerization. Among approximately 40 dhAAs found in the natural product inventory, dehydroalanine (Dha) and dehydrobutyrine (Dhb) are the most abundant. Dha is the simplest dehydro-α-amino acid, or α-dhAA, without any geometrical isomers, while its re-arranged isomer, 3-aminoacrylic acid (Aaa or ΔβAla), is the simplest dehydro-β-amino acid, or β-enamino acid, and displays E/Z isomerism. Dhb is the simplest α-dhAA that exhibits E/Z isomerism. The Z-isomer of Dhb (Z-Dhb) is sterically favourable and is present in the majority of naturally occurring peptides containing Dhb residues. Dha and Z-Dhb motifs are commonly found in ribosomally synthesized and post-translationally modified peptides (RiPPs). In the last decade, the formation of Dha and Dhb motifs in RiPPs has been extensively investigated, which will be briefly discussed in this review. The formation of other dhAA residues in natural products (NPs) is, however, less understood. In this review, we will discuss recent advances in the biosynthesis of peptidyl NPs containing unusual dhAA residues and cryptic dhAA residues. The proposed biosynthetic pathways of these natural products will also be discussed.

Ball milling‐assisted exfoliation and deposition to prepare few‐layer graphene/PVC nanocomposites with enhanced thermal stability

AbstractIt is still a great challenge to prepare high‐performance graphene/polymer nanocomposites by fully utilizing the large surface area, high tensile strength, and high thermal stability. Herein, a simple but efficient approach based on ball milling was developed to in situ exfoliate graphite into single‐layer graphene and simultaneously deposit them onto polyvinyl chloride (PVC) surface. Graphene/PVC nanocomposites were prepared via the plasticized molding and followed by hot pressing. Resulting from incorporation of highly exfoliated and evenly distributed graphene nanosheets, the obtained graphene/PVC nanocomposites displayed a significantly enhanced thermal stability. In contrast with neat PVC, the temperature of maximum weight loss (Tmax), glass transition temperature (Tg), and residual content of composite with 2.0 wt% graphene were increased by 10, 13°C, and 4.4%, respectively. Based on the deep analysis on heat releasing behavior and structure of residue, we proposed the related enhancing mechanism. Large‐area and highly exfoliated graphene sheets effectively inhibited the heat/mass transfer in composite system and prevented the degradation of PVC, as well as promoted the compact residue formation from polymer itself at high temperatures. In short, this work provided an environmentally friendly strategy to prepare high‐performance graphene/polymer nanocomposites with using low additive amount of single‐layer graphene.Highlights A simple graphite exfoliation method based on ball milling was proposed. Strong shearing and compact force induce graphene exfoliation and deposition. Graphene/PVC nanocomposites with enhanced thermal stability was prepared.

Reusing blended leach residue by flash sintering method

AbstractIn this study, the effects of different sintering methodology on grain formation, density, and hardness of blended leach residue (B‐LR) pellets is investigated. For the first time, the flash sintering (FS) method, an environmentally friendly process, is used to make multiphase ceramic composites using B‐LR under 100 V/mm at 675C. The outcomes of this study revealed that the FS process is faster and more energy‐efficient than the conventional sintering (CS) methods performed at 800°C for 4 h. The formation of abnormal grain growth is prevented by FS in B‐LR material composition after it is exposed to a max power absorption 61.4 mW/mm3 and whole FS is completed less than 100 s. Besides, FS method does not lead to any melting on grain boundaries due to excessive joule heating, compared with the CS sample. It is noted that FS also provides better density and hardness values for this material system along with compositional integrity in this multiphase system. The significant outcome of this study is reducing lead volatility and emission by decrement on the sintering temperature. Ultimately, this study has planned the practicality of reusage and recycle of this material with green, safe, and eco‐friendly methods.

Insights into the Fungicide Prothioconazole and Its Metabolite in Wheat: Residue Behavior and Risk Assessment

To clarify the residue formation of prothioconazole and its main metabolite in wheat plants, the uptake, translocation, and metabolism of prothioconazole in wheat roots and leaves were investigated by nutrient solution culture and the spraying method. The results showed that prothioconazole and its metabolites showed a trend of increasing and then decreasing in wheat plants under two treatment methods, and the concentration of prothioconazole and its metabolites was higher in the high-concentration group (5000 μg/mL) than in the low-concentration group (1000 μg/mL). The transferability from stem to leaf was stronger than that from root to stem. In the nutrient solution culture, prothioconazole and its metabolites were mainly enriched in wheat roots. The concentration of prothioconazole in wheat roots increases with the increase in prothioconazole concentration and was significantly higher than the prothioconazole concentration on stems and leaves. In wheat leaves in the spraying method, prothioconazole and its metabolites were conducted from leaves to stems and roots up to the nutrient solution. Prothioconazole-desthio was detectable in wheat nutrient solution, while prothioconazole was not detected. Analysis of actual samples of 9 wheat grains and 28 flours showed that the residues of prothioconazole and its metabolites met the maximum residue limit (0.1 mg/mL) set in China and by the Codex Alimentarius Commission. The results will provide a theoretical basis for the scientific use of prothioconazole and food security assurance.

Enhanced flame‐retardant performance of rigid polyurethane foam by using APTES‐MMT and ATH mixed intumescent coatings

AbstractThe design of environment‐friendly fireproof rigid polyurethane foams (RPUFs) that completely prevent ignition or the spread of fires is important for energy conservation and emission reductions. In this paper, an intumescent flame‐retardant coating was prepared and coated onto the surface of a RPUF to improve its flame retardancy. Vertical combustion experiments (UL‐94) showed that, compared with the pure RPUF, a RPUF coated with the expansion coating successfully self‐extinguished without a droplet formed after ignitor removal. Thermogravimetric analyses showed that the expanded coating effectively increased the rate of carbon residue formation. Cone calorimetry showed that when the pigment‐to‐binder ratio was 3.5:1, with 5% modified montmorillonite, 6% aluminum hydroxide, and 4% titanium dioxide, the intumescent coating effectively reduced the heat release rate and total heat release of the RPUF. Remarkably, the smoke release rate and total exhaust gas volume showed that the expanded coating provided obviously enhanced smoke suppression. Therefore, the flame retardancy and toxic smoke suppression provided by the RPUF thermal insulation material is essential and very useful for healthy development of human society and the environment.

The Interaction of Pesticides with Humin Fractions and Their Potential Impact on Non-Extractable Residue Formation.

The constant influx of pesticides into soils is a key environmental issue in terms of their potential retention in the soil, thus reducing their negative impact on the environment. Soil organic matter (SOM) is an important factor influencing the environmental fate of these substances. Therefore, the aim of this research was to assess the chemical behavior of pesticides (flufenacet, pendimethalin, α-cypermethrin, metazachlor, acetamiprid) toward stable soil humin fractions (HNs) as a main factor affecting the formation of non-extractable residues of agrochemicals in soil. This research was conducted as a batch experiment according to OECD Guideline 106. For this purpose, HNs were isolated from eight soils with different physicochemical properties (clay content = 16-47%, pHKCl = 5.6-7.7, TOC = 13.3-49.7 g·kg-1, TN = 1.06-2.90 g·kg-1, TOC/TN = 11.4-13.7) to reflect the various processes of their formation. The extraction was carried out through the sequential separation of humic acids with 0.1 M NaOH, and then the digestion of the remaining mineral fraction with 10% HF/HCl. The pesticide concentrations were detected using GC-MS/MS. The pesticides were characterized based on the different sorption rates to HNs, according to the overall trend: metazachlor (95% of absorbed compound) > acetamiprid (94% of absorbed compound) > cypermethrin (63% of partitioning compound) > flufenacet (39% of partitioning compound) > pendimethalin (28% of partitioning compound). Cypermethrin and metazachlor exhibited the highest saturation dynamic, while the other agrochemicals were much more slowly attracted by the HNs. The obtained sorption kinetic data were congruous to the pseudo-first-order and pseudo-second-order models related to the surface adsorption and interparticle diffusion isotherm. The conducted research showed that the processes of pesticide sorption, apart from physicochemical phenomena, are also affected by the properties of the pollutants themselves (polarity, KOC) and the soil properties (SOM content, clay content, and pHKCl).

Solvothermal liquefaction of Tetra Pak waste into biofuels and Al2O3-carbon nanocomposite

This study explores a novel solvothermal disposal technique of Tetra Pak waste for the co-synthesis of value-added bio-oil and alumina-carbon nanocomposite. The impact of residence time (10–50 min.), temperature (240–360 °C), and substrate-to-solvent ratio (1:4–1:10) on the solvothermal liquefaction of Tetra Pak waste with supercritical ethanol were investigated on a batch scale. Initially rise in operating temperature and residence time positively influenced the bio-oil yield. However, a decline in yield was seen beyond a certain point. A higher substrate-to-solvent ratio enhanced the bio-oil yield as the solvent demonstrated its effective capabilities to depolymerize the feedstock. The favorable condition for the highest bio-oil yield (34.41 %) and HHV (30.51 MJ/Kg) were found to be at 320 °C, 30 min, and a substrate-to-solvent ratio of 1:10. The synergetic effect of solvent (ethanol) and aluminium present in Tetra Pak leads to the formation of in-situ generated active hydrogen that enhances the bio-oil yields and inhibits residue formation. XRD and XPS analysis confirms the transformation of aluminium from (Al (0)) to (Al (+3)) in the presence of ethanol forming in-situ generated alumina-carbon nanocomposite that has the potential to be used as a catalyst. NMR, GC–MS, and FTIR analysis confirmed the richness of bio-oil in various organic compounds including alcohol, esters, ketones, ethers, acids, and phenols. The recovered ethanol from the process exhibits a significant potential to be reused as a solvent or as a fuel additive.

A Multi-Material Flame-Retarding System Based on Expandable Graphite for Glass-Fiber-Reinforced PA6.

A synergistic multi-material flame retardant system based on expandable graphite (EG), aluminum diethylphosphinate (AlPi), melamine polyphosphate (MPP), and montmorillonite (MMT) has been studied in glass-fiber-reinforced polyamide 6 (PA6). Analytical evaluations and fire performances were evaluated using coupled thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) as well as cone calorimetry, UL-94 fire testing, and limiting oxygen index (LOI). A combination of EG/AlPi/MPP/MMT has been shown to provide superior flame-retarding properties when integrated at 20 wt.% into glass-fiber-reinforced PA6 (25 wt.%), achieving UL-94 V0 classification and an oxygen index of 32%. Strong residue formation resulted in low heat development overall, with a peak heat release rate (pHRR) of 103 kW/m2, a maximum of average heat release rate (MAHRE) of 33 kW/m2, and deficient total smoke production (TSP) of 3.8 m2. Particularly remarkable was the structural stability of the char residue. The char residue could easily withstand an areal weight of 35 g/cm2, showing no visible deformation.

Exogenous delivery of dsRNA for management of mungbean yellow mosaic virus on blackgram.

Exogenous application of dsRNA molecules targeting MYMV genes offers a promising approach to effectively mitigate yellow mosaic disease in blackgram, demonstrating potential for sustainable plant viral disease management. The exogenous application of double-stranded RNA (dsRNA) molecules to control plant viral diseases is gaining traction due to its advantages over conventional methods, such as target specificity, non-polluting nature, and absence of residue formation. Furthermore, this approach does not involve genome modification. In this study, dsRNA molecules targeting the coat protein gene (dsCP) and replication initiator protein gene (dsRep) of mungbean yellow mosaic virus (MYMV) were synthesised using an in vitro transcription method. To evaluate the effectiveness of dsRNA treatment, blackgram plants exhibiting MYMV symptoms at the first trifoliate stage were subjected to exogenous application of dsRNA. Second, third, and fourth trifoliate leaves, which emerged at 7, 15, and 21days after dsRNA application, respectively, were monitored for MYMV symptoms. Remarkably, a significant reduction in yellow mosaic disease (YMD) symptoms was observed in the newly emerged trifoliate leaves of MYMV-infected blackgram plants after treatment with dsRNA targeting both gene regions. This reduction was evident as a decrease in the intensity of yellow mosaic coverage on the leaf lamina compared to control. dsCP effectively reduced the MYMV titre in the treated plants for up to 15days. However, dsRep demonstrated greater efficiency in conferring resistance to MYMV at 15days post-application. These findings were supported by quantitative real-time PCR analysis, where the observed Ct values for DNA extracted from dsRep-treated plants were significantly higher compared to the Ct values of DNA from dsCP-treated plants at 15days post-application. Similarly, higher viral copy numbers were observed in dsCP-treated plants 15days after dsRNA treatment, in contrast to plants treated with dsRep.

Antibiotic Residues in fresh Chicken, Fish and Beef Meat samples in ‎Maiduguri, Nigeria

Prudent use of antibiotics in animal industry is essential for treatment of diseases and preventive measure. However, uncontrolled use of these agents in large amounts and consistently could result in the formation of antibiotic residues in muscle and organs of animal. This study aimed to determine the occurrence of antibiotic residue in fresh meats in Maiduguri. A cross-sectional study was conducted from September 2022 to December 2022 to determine the antibiotic residue in 3 sources of meat samples. A total of 150 fresh meat samples (chicken, fish and beef) were collected from different sale points Maiduguri, and analyzed using a Premi® Test kit (R-Biopharm AG, Germany), a microbial screening commercial test kit for the detection of antibiotic residues. The results showed an overall antibiotic residue of 127/150 (84.7%) meat samples were positive for antibiotic residues. High antibiotic residues was found in Chicken meats 47/50 (94%), followed by fish 43/50 (86%), and beef 37/50 (74%). The results in this study show the presence of antibiotic residues in meat. Therefore, it is recommended that effective legislation on antibiotic use in animals should be enforced.

Fermented biochar has a markedly different effect on fate of pesticides in soil than compost, straw, and a mixed biochar-product

Current knowledge about how biochars affect the fate of pesticides in soil is based on studies that used pure biochars. After finding that an additional biological post-pyrolysis treatment, such as co-composting or lactic fermentation, is required for biochars for superior performance in temperate arable soils, a knowledge gap formed of how such further processed biochar products would affect the fate of pesticides in soil. This study compared the effects of a novel fermented biochar alone or mixed with biogas residues on the fate of two pesticides, 4-chloro-2-methylphenoxyacetic acid (MCPA) and metalaxyl-M, in a temperate arable soil to the traditional organic amendments wheat straw and compost. The fate of 14C-labeled MCPA was markedly affected in different ways. Fermented biochar effectively reduced the water-extractability and mineralization due to adsorption that was comparable to adsorption strengths reported for pure biochars. However, this effect was weak for the biochar mixed with biogas residues. Straw reduced water-extractable amounts due to increased biodegradation and formation of likely biogenic non-extractable residues of MCPA. In contrast, compost decelerated mineralization and increased the water solubility of the MCPA residues due to released dissolved organic matter. The amendments' effects were minor regarding 14C-metalaxyl-M, except for the fermented biochar which again reduced water-extractability and delayed degradation due to adsorption. Thus, the effects of the organic amendments differed for the two pesticide compounds with only the fermented biochar's effect being similar for both. However, this effect was no longer present in the mixed product containing 20% biochar. Our findings clearly show that biologically treated biochar-containing products can affect the fate of pesticides in soil very differently, also when compared to traditional organic amendments. Such impacts and their desirable and undesirable ecotoxicological implications need to be considered before the large-scale application of biochars to temperate arable soils.

Evaluation of the acute toxicity by Artemia salina of hydroxyapatite nanoparticles obtained via sol-gel in an aqueous medium without using additives

Hydroxyapatite (Hap) is one of the most important calcium phosphate bioceramics applied to bone tissue regeneration. Synthesizing Hap nanoparticles from easily accessible and low-cost alternative sources of calcium precursors remains a challenge, as well as defining an ideal and reproducible synthesis route without using additives to control the pH of the reaction and entirely performed at room temperature. This study proposes a route for the synthesis of hydroxyapatite by the sol-gel method without the addition of additives for pH control, carried out at room temperature. The Hap samples were characterized by FTIR, XRD, SEM, and BET. The synthesized Hap presented a spherical morphology without the formation of unwanted phases or residues. Samples calcined at 600 and 750 °C resulted in stoichiometric hydroxyapatite with 100% purity and average particle sizes of 24 and 53 nm, respectively. On the other hand, the samples calcined at 900 and 1050 °C presented a specific content of β-calcium phosphate and average particle sizes of 118 and 732 nm, respectively. Acute toxicity was evaluated by Artemia salina nauplii instar I and II for 24 and 48 h of exposure. The tests were conducted on 10, 100, and 1000 ppm of Hap dissolutions. The highest death rate and more significant morphological alterations were observed in A. salina nauplii instar II, exposed to Hap at a concentration of 1000 ppm for 48 h.

Fate and transformation of uniformly 14C-ring-labeled bisphenol S in different aerobic soils

Bisphenol S (BPS), being structurally similar to bisphenol A (BPA), has been widely used as an alternative to BPA in industrial applications. However, in-depth studies on the environmental behavior and fate of BPS in various soils have been rarely reported. Here, 14C-labeled BPS was used to investigate its mineralization, bound residues (BRs) formation and extractable residues (ERs) in three soils for 64 days. Significant differences were found in the dissipation rates of BPS in three soils with different pH values. The dissipation of BPS followed pseudo first-order kinetics with half-lives (T1/2) of 15.2 ± 0.1 d, 27.0 ± 0.2 d, 180.4 ± 5.3 d, and 280.5 ± 3.3 d in the alkaline soil (fluvo-aquic soil, FS), the neutral soil (cinnamon soil, CS), the acidic soil (red soil, RS), and sterilized cinnamon soil (CS-S), respectively. The mineralization and BRs formation contributed the most to the dissipation of BPS in soil. BPS was persistent in acidic soil, and may pose a significant threat to plants grown in acidic soils. Additionally, soil microorganisms played a key role in BPS degradation, and the organic matter content might be a major factor that promotes the adsorption and degradation of BPS in soils. Two transformed products, P-hydroxybenzenesulfonic acid and methylated BPS were identified in soils. This study provides new insights into the fate of BPS in various soils, which will be useful for risk assessments of BPS in soil.